Slow-release fertilizers by biochar and zeolite enriched by treated wastewater for nutrient recovery

The recovery of nutrients from wastewater and their subsequent reuse as fertilizers is desirable to counteract soil fertility decrease, to avoid eutrophication of superficial water bodies, and to push the circular economy. Zeolite and biochar are two adsorbents widely used for ammonium and phosphorus recovery from wastewater. However, after their enrichment with nutrients, they can be applied to the soil thus acting as slow-release fertilizers. This chapter after describing the main properties of zeolite and biochar and the main mechanisms by which they adsorb nutrients from wastewater, evaluates their potential in acting as slow-release fertilizers. To this aim, already published data and results from ongoing activity within the Wider Uptake project are reported and discussed. It is concluded that enriched-zeolite and -biochar are of key importance to improve soil productivity by addressing nitrogen and phosphorous uptake as major requirements for plant growth and controlling nutrient losses through leaching processes.